Users of computer networks such as "Internet" by way of Public Switched Telephone Networks (PSTN) are increasing in phenomenal numbers; the majority of users access "Internet" by dial-up telephone connection.
As taught in a related U.S. patent application Ser. No. 60/048,325, the entire specification of which is incorporated by reference, many problems in managing IP-based data service through PSTN access (PSTN switch congestion, such as need for increasing trunking resources, an increased modem pool management complexity, and a need for increasing number of ISP access lines) can be addressed, at least in part, via deployment of a centralized network controller (NC) and a modem wholesaling function in the access network. Benefits of such an approach include direct PSTN congestion relief; flexible tariffing of modem wholesaling services into ISPs, economy of scale through modem pooling to multiple ISPs; network based real-time control of services (ISP port limiting, ISP home gateway load balancing); real-time access to network-wide service information, call/event logs, and operational measurements; and centralized control for invocation of administrative state on access network elements. Although the related patent does allude to use of Common Channel Signalling System Number Seven (CCS7) based control of call setup into the NAS, Network Access Server, NAS specific details of how this approach functions were not addressed. Further, the related application does not address out-of-band call setup into the NAS via the existing PSTN CCS7 infrastructure. As well, an architecture for interworking a CCS7 controlling agent, network controller, and existing telecommunications networks for the purposes of services interworking was also not addressed.
Within the PSTN (hereafter including the ISDN), CCS7 provides a highly robust and reliable infrastructure for control of narrowband (up to 64 kbps) circuit-switched basic call setup and supplementary services (e.g., mobility, freephone, calling name/number display). For example, within North America the CCS7 specifications include T1.113.x for ISDN User Part Call Control Signalling, T1.112.x for Signalling Connection and Control Part (SCCP) connection-oriented and connectionless services, T1.111.x for Message Transfer Part network layer services and for link layer services. The CCS7 specifications also provide appropriate support for ISDN-based data services (restricted and unrestricted digital information) through specification of appropriate bearer services and ISDN information element handling. Thus, CCS7 can be employed within an ISDN to support a digital data service for IP-related services. However, the CCS7 specifications do not address procedures for IP-based data services and their interworking with the PSTN (e.g., address translation, information element mapping). An appropriate architecture is required to address this interworking issue.
Within Internet Protocol based data networks (both the internet and intranets (e.g., corporate networks)) and specifications, a variety of network access alternatives 35 are possible (e.g., PSTN-based dial-up access, private line, cable modem). For dial-up based access from the PSTN, a point-to-point modem protocol (e.g., Serial Line Interface Protocol (SLIP), Point-to-Point Protocol (PPP)) is used to establish a data path over the analog physical layer access. One placement of the network-side modem to terminate the point-to-point modem protocol is to provide a modem pool platform (NAS) accessed from the PSTN via an ISDN Primary Rate Interface (PRI) digital interface. PRI is a User Network Interface (UNI) supporting one in-band signalling channel and 23 bearer channels (i.e., 23 narrowband modem calls can be terminated within the modem pool platform for each PRI interface). This implementation has some shortcomings based upon concerns such as provisioning, tariffing, network ownership, and maintenance. Since PRI is a UNI, the point of interworking between the PSTN and modem termination is explicitly visible and the PSTN takes the role of an access user of the data network (i.e., via a UNI). This is inconvenient if the PSTN network provider is also providing the modem termination function. Further, the IP specifications also do not adequately address an architecture and procedures for IP-based data services and their interworking with the PSTN (e.g., address translation, information element mapping).
It is desirable to support an interworking between the PSTN and IP-based data networks in a transparent fashion based upon a Network-to-Network (NNI) interface. As explained above, the existing CCS7 and IP specifications do not adequately address a method and architecture through which to use the existing CCS7 infrastructure and traditional telephony NNI trunking interfaces (e.g., T1 trunks) to set up and control a data network (e.g., IP) call. It is also desirable to identify an appropriate architecture to enable further interworking between existing networks (PSTN, mobility networks (e.g., GSM)) and IP-based data networks for services interworking.
A flexible and efficient means to interwork the existing PSTN infrastructure with data networks for IP-related call control, and to interwork IP-based data networks with PSTN and other networks for services interworking, is desirable.